1. Field of the Invention
The present invention concerns apparatus for cleaning or otherwise treating a plurality of articles as for example beverage cans or the like, or other more or less fragile bodies in a continuous and uninterrupted operation.
2. Description of the Prior Art
Apparatus suitable for such purposes has been disclosed in the patent to Marvin K. Rohrs, U.S. Pat. No. 4,092,991 granted June 6, 1978. As there seen, such apparatus may comprise a lower perforated conveyor in the form of an endless belt for transporting the articles that are to be cleaned or otherwise treated through the washing machine. An overhanging so-called "hold down" conveyor in the form of a wire mesh belt is also provided for controlling the position of the cans or other articles during the high pressure spray cycles: that is, to maintain the cans in the proper position so that the high pressure sprays will do their job efficiently and economically. Additionally, such "hold down" conveyor is to prevent damage to the cans that might result from tipping or tilting the same as they travel uninterruptedly through the apparatus assembly.
In the Rohrs patent, above mentioned, it is said that the machine basically comprises the lower article supporting conveyor and the overhead hold down conveyor: the remainder of the machine being largely conventional and comprising the usual sprays of chemicals and cleaning materials for cleaning, rinsing or otherwise treating the cans or other articles being washed or treated.
In the prior art, and in the Rohrs patent as well, the length of the hold down conveyor is much shorter than that of the lower can transporting carrier or conveyor. In fact, generally a separate independent hold down belt overlies the pre-rinse, spray bar, prewash and wash tanks individually, at or near the beginning of the continuous cycle which normally may subject the articles travelling therethrough to the steps of pre-rinse, pre-wash, wash, first rinse, treatment, second rinse, and diionized water rinse, with intermediate zones or sections for draining and blowing off to remove excess treating liquids.
With the arrangement just described, wherein the hold down conveyor overlies only a relatively short portion of the entire reach or length of the multi-stage continuous apparatus, certain problems in the industry have resulted. That is to say a rapid deterioration of the hold down belt is being experienced in the wash section of the washer due to the continuous exposure of this hold down belt to the action of the erosive and corrosive wash solution. The hold down belt does not get rinsed as does the main belt, that is the article transporting or carrier belt, and it is continuously subject to the wash chemistry. As a result it has been found necessary to replace the hold down belt much more often than is the case with the longer transporting belt or carrier.
Moreover, the current trend is to lower temperature cleaners and the use of higher pressures in the wash section. Lower temperature cleaners become very active and erosive and corrosive if higher than the recommended temperatures are used. On the other hand, if the cleaners are used at the higher end of the recommended temperature scale, they are naturally enough more effective and along with the higher pressure they provide a better cleaning job.
In addition, the use of high pressure rinsing is now recognized for its advantages in providing cans with improved final cleanliness. This means cans clean of all residues from washing and treatment chemistry. The use of high pressure rinsing in turn demands the control of the can while it is subject to these intense spray conditions. Under these conditions the use of a hold down in these areas provides the control necessary when using these higher pressures.